METHOD FOR PRODUCING LUMINOUS PIGMENT

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PROBLEM TO BE SOLVED : To provide a method for producing a luminous pigment excellent in afterglow brightness characteristics and water resistance. SOLUTION : Provided is a method for producing a luminous pigment comprising : (step A) where luminous pigment raw material powder obtained by doping a rare-earth element into an alkaline-earth metal oxide is prepared; (step B) where this raw material powder is added to an aqueous solution containing inorganic acid and a phosphate, stirring is performed, and the same is subjected to acid/phosphate treatment; and (step C) where the luminous pigment obtained by the treatment is cleaned with water or is subjected to neutralization treatment with an alkali aqueous solution and is thereafter subjected to drying. When the neutralization treatment is performed using the alkali aqueous solution, the pH of the luminous pigment-containing is preferably controlled to the range of 6.8 to 7.2. As the inorganic acid, chloric acid, nitric acid or sulfuric acid is preferable, as the phosphate, sodium dihydrogen phosphate, ammonium dihydrogen phosphate or diammonium hydrogen phosphate is preferable, as the alkaline-earth metal oxide, SrAl2O4 or Sr4Al14O25 is preferable, and, as the rare earth element, a lanthanoid rare earth element is preferable. SELECTED DRAWING : None COPYRIGHT : (C)2017, JPO&INPIT